1. Field of the Invention
The invention relates to a wet cleaning solution, and in particular to a wet cleaning solution suitable for cleaning hydrophobic semiconductor substrates after chemical mechanical polishing (CMP).
2. Description of the Related Art
As the geometry of semiconductor devices continues to decrease, trace amounts of contaminants remaining on a semiconductor substrate have more significant effects on device performance and yield, demanding much stricter contamination control. Therefore, cleaning with a variety of liquid cleaners is conducted in individual steps in processes for manufacturing a semiconductor device.
For example, in the steps for manufacturing a multilayered semiconductor device, CMP is common for leveling an insulating film or forming a damascene interconnection, with adequately effective removal of contaminants required during cleaning following such process. After CMP, the wafer surface is contaminated with a large amount of particles or metallic contaminants. The particles originate with the polishing particles (inorganic particles such as silica or alumina) in the slurry, and the metallic contaminants are derived from interconnection material such as copper, polished during formation of damascene interconnection or a via metal. Thus, before continuing the construction of the integrated circuits, a post-CMP cleaning process is necessary to remove contaminants such as particles and metallic contaminants while preventing damage to a metal interconnection or insulating layer exposed on a substrate surface.
The interconnection delay has become a major concern in modern IC (Integrated Circuit) design. Thus, the interconnection delay is conventionally reduced by using a low-resistivity material such as copper (Cu) as an interconnection material and further using a low dielectric-constant (low-k) material in place of a conventional silicon dioxide as a material for an interlayer insulating film or an inter-interconnection insulating film.
Such a low-k material is, however, less wettable, i.e., more hydrophobic, than the conventional silicon oxide. Therefore, hydrophobic substrates are more difficult to clean than hydrophilic substrates, due to the poor wettability of aqueous cleaning solutions on hydrophobic low-k dielectric substrates. Also, the efficiency of chemical residues removed by deionized water rinsing is very low. Watermarks or residues are commonly observed on the hydrophobic surfaces during drying, which may cause subsequent device failure. The semiconductor industry is increasing the use of low-k dielectric wafers and, hence, much attention has been directed to improved methods for cleaning hydrophobic substrates.
Accordingly, a need exists for an improved cleaning solution and method for cleaning hydrophobic substrates.